Gas sensor

A gas sensor, comprising:

• a housing having an open portion at one side of the housing;
• a circuit board securely provided inside the housing, the circuit board defining a gas sensing space in the housing that communicates with the open portion of the housing, and the circuit board having a sensing element located in the gas sensing space and configured to sense a specific gas;
• a holder provided inside the gas sensing space, and fixed to the housing, the holder having a through hole communicating with the open portion of the housing;
• and
• a filter provided inside the gas sensing space, and coupled to the holder or the housing so as to cover the through hole or the open portion,
• wherein the filter is provided between the housing and the holder and covers both the open portion of the housing and the through hole at the same time, the filter defining the gas sensing space while being spaced apart from the circuit board,
• wherein the housing comprises a support that is extended to protrude from a bottom surface at a periphery of the open portion toward the circuit board, and
• wherein the holder is fixed to the housing while being inserted in the support.